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Room temperature single-step synthesis of metal decorated boron-rich nanowires via laser ablation
Mark H. Rummeli,Barbara Trzebicka,Gianaurelio Cuniberti,Thomas Gemming,Alicja Bachmatiuk,Ignacio G. Gonzalez-Martine 나노기술연구협의회 2019 Nano Convergence Vol.6 No.14
Hybrid nanostructures, such as those with nanoparticles anchored on the surface of nanowires, or decorated nanowires, have a large number of potential and tested applications such as: gas sensing, catalysis, plasmonic waveguides, supercapacitors and more. The downside of these nanostructures is their production. Generally, multi-step synthesis procedures are used, with the nanowires and the nanoparticles typically produced separately and then integrated. The few existent single-step methods are lengthy or necessitate highly dedicated setups. In this paper we report a single-step and rapid (ca. 1 min) laser ablation synthesis method which produces a wide variety of boron-rich decorated nanowires. Furthermore, the method is carried at room temperature. The synthesis process consists on a filamentary jet ejection process driven by pressure gradients generated by the ablation plume on the rims of the irradiation crater. Simultaneously nanoparticles are nucleated and deposited on the filaments thus producing hybrid decorated nanowires.
Kim, Beom Seok,Lee, Namkyu,Thota, Subhash,Gemming, Thomas,Cho, Hyung Hee Elsevier BV * North-Holland 2019 Applied Surface Science Vol.496 No.-
<P><B>Abstract</B></P> <P>Selective laser melting (SLM) is a promising additive manufacturing technique arising from glassy metal characteristics of treated medium. When creating novel compositions of materials and intricate workpieces, reliable thermal designs should be implemented based on well-understood heat transfer characteristics on matierlas to be used. Herein, we investigate local and overall heat transfer characteristics of SLM processes and investigate the principal parameters related to the magnituge of a radiative heating power and its exposure time. We present how to exert their influence upon local melting and sequential solidification of copper powder bed. The local solid media reach a quasi-equilibrium state in even 1 ms with the incident powers of 50, 100, and 200 W. The anisotropic expansion of the molten pool is governed by a thermally-induced Marangoni flow. As the power is increased, the Marangoni factor increases linearly up to 853.7%. Consequential heat transfer characteristics tell us that unconditional input power should be avoided to prohibit the detrimental effect; the radiative heating power should be confined for thermalization of a target domain and for that preventing the evaporation of a material. These approaches from material science to heat transfer can be used to develop a platform for SLM processes guaranteeing its feasibility and applicability.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Suggestion of thermal design for SLM process through analytical approach and simulation </LI> <LI> Extraction of Marangoni factor to evaluate the thermally-induced effect <I>via</I> SLM process </LI> <LI> Revealing heat transfer characteristics during SLM process causing detrimental effect on additive manufacturing products </LI> </UL> </P>
Functionalization of Ti-40Nb implant material with strontium by reactive sputtering
Markus Göttlicher,Marcus Rohnke,Yannik Moryson,Jürgen Thomas,Joachim Sann,Anja Lode,Matthias Schumacher,Romy Schmidt,Stefan Pilz,Annett Gebert,Thomas Gemming,Jürgen Janek 한국생체재료학회 2017 생체재료학회지 Vol.21 No.4
Background: Surface functionalization of orthopedic implants with pharmaceutically active agents is a modern approach to enhance osseointegration in systemically altered bone. A local release of strontium, a verified bone building therapeutic agent, at the fracture site would diminish side effects, which could occur otherwise by oral administration. Strontium surface functionalization of specially designed titanium-niobium (Ti-40Nb) implant alloy would provide an advanced implant system that is mechanically adapted to altered bone with the ability to stimulate bone formation. Methods: Strontium-containing coatings were prepared by reactive sputtering of strontium chloride (SrCl2) in a self-constructed capacitively coupled radio frequency (RF) plasma reactor. Film morphology, structure and composition were investigated by scanning electron microscopy (SEM), time of flight secondary ion mass spectrometry (ToF-SIMS) and X-ray photoelectron spectroscopy (XPS). High-resolution transmission electron microscopy (HR-TEM) was used for the investigation of thickness and growth direction of the product layer. TEM lamellae were prepared using the focused ion beam (FIB) technique. Bioactivity of the surface coatings was tested by cultivation of primary human osteoblasts and subsequent analysis of cell morphology, viability, proliferation and differentiation. The results are correlated with the amount of strontium that is released from the coating in biomedical buffer solution, quantified by inductively coupled plasma mass spectrometry (ICP-MS). Results: Dense coatings, consisting of SrOxCly, of more than 100 nm thickness and columnar structure, were prepared. TEM images of cross sections clearly show an incoherent but well-structured interface between coating and substrate without any cracks. Sr2+ is released from the SrOxCly coating into physiological solution as proven by ICP-MS analysis. Cell culture studies showed excellent biocompatibility of the functionalized alloy. Conclusions: Ti-40Nb alloy, a potential orthopedic implant material for osteoporosis patients, could be successfully plasma coated with a dense SrOxCly film. The material performed well in in vitro tests. Nevertheless, the Sr2+ release must be optimized in future work to meet the requirements of an effective drug delivery system.
Vertical Graphene Growth from Amorphous Carbon Films Using Oxidizing Gases
Bachmatiuk, Alicja,Boeckl, John,Smith, Howard,Ibrahim, Imad,Gemming, Thomas,Oswald, Steffen,Kazmierczak, Wojciech,Makarov, Denys,Schmidt, Oliver G.,Eckert, Juergen,Fu, Lei,Rummeli, Mark H. American Chemical Society 2015 JOURNAL OF PHYSICAL CHEMISTRY C - Vol.119 No.31
<P>Amorphous carbon thin films are technologically important materials that range in use from the semiconductor industry to corrosion-resistant films. Their conversion to crystalline graphene layers has long been pursued; however, typically this requires excessively high temperatures. Thus, crystallization routes which require reduced temperatures are important. Moreover, the ability to crystallize amorphous carbon at reduced temperatures without a catalyst could pave the way for practical graphene synthesis for device fabrication without the need for transfer or post-transfer gate deposition. To this end we demonstrate a practical and facile method to crystallize deposited amorphous carbon films to high quality graphene layers at reduced annealing temperatures by introducing oxidizing gases during the process. The reactive gases react with regions of higher strain (energy) in the system and accelerate the graphitization process by minimizing criss-cross-linkages and accelerating C–C bond rearrangement at defects. In other words, the movement of crystallite boundaries is accelerated along the carbon hexagon planes by removing obstacles for crystallite coalescence.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-31/acs.jpcc.5b05167/production/images/medium/jp-2015-05167v_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b05167'>ACS Electronic Supporting Info</A></P>
A size dependent evaluation of the cytotoxicity and uptake of nanographene oxide
Mendes, Rafael Gregorio,Koch, Britta,Bachmatiuk, Alicja,Ma, Xing,Sanchez, Samuel,Damm, Christine,Schmidt, Oliver G.,Gemming, Thomas,Eckert, Jü,rgen,Rü,mmeli, Mark H. The Royal Society of Chemistry 2015 Journal of Materials Chemistry B Vol.3 No.12
<P>Graphene oxide (GO) has attracted great interest due to its extraordinary potential for biomedical application. Although it is clear that the naturally occurring morphology of biological structures is crucial to their precise interactions and correct functioning, the geometrical aspects of nanoparticles are often ignored in the design of nanoparticles for biological applications. A few <I>in vitro</I> and <I>in vivo</I> studies have evaluated the cytotoxicity and biodistribution of GO, however very little is known about the influence of flake size and cytotoxicity. Herein, we aim at presenting an initial cytotoxicity evaluation of different nano-sized GO flakes for two different cell lines (HeLa (Kyoto) and macrophage (J7742)) when they are exposed to samples containing different sized nanographene oxide (NGO) flakes (mean diameter of 89 and 277 nm). The obtained data suggests that the larger NGO flakes reduce cell viability as compared to smaller flakes. In addition, the viability reduction correlates with the time and the concentration of the NGO nanoparticles to which the cells are exposed. Uptake studies were also conducted and the data suggests that both cell lines internalize the GO nanoparticles during the incubation periods studied.</P>
Pang, Jinbo,Bachmatiuk, Alicja,Fu, Lei,Yan, Chenglin,Zeng, Mengqi,Wang, Jiao,Trzebicka, Barbara,Gemming, Thomas,Eckert, Juergen,Rummeli, Mark H. American Chemical Society 2015 The Journal of Physical Chemistry Part C Vol.119 No.23
<P>One of the more common routes to fabricate graphene is by chemical vapor deposition (CVD). This is primarily because of its potential to scale up the process and produce large area graphene. For the synthesis of large area monolayer Cu is probably the most popular substrate since it has a low carbon solubility enabling homogeneous single-layer sheets of graphene to form. This process requires a very clean substrate. In this work we look at the efficiency of common pretreatments such as etching or wiping with solvents and compare them to an oxidation treatment at 1025 °C followed by a reducing process by annealing in H<SUB>2</SUB>. The oxidation/reduction process is shown to be far more efficient allowing large area homogeneous single layer graphene formation without the presence of additional graphene flakes which form from organic contamination on the Cu surface.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpccck/2015/jpccck.2015.119.issue-23/acs.jpcc.5b03911/production/images/medium/jp-2015-03911k_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp5b03911'>ACS Electronic Supporting Info</A></P>
Gonzalez-Martinez, Ignacio G.,Gorantla, Sandeep M.,Bachmatiuk, Alicja,Bezugly, Viktor,Zhao, Jiong,Gemming, Thomas,Kunstmann, Jens,Eckert, Jü,rgen,Cuniberti, Gianaurelio,Rü,mmeli, Mark H. American Chemical Society 2014 NANO LETTERS Vol.14 No.2
<P>Despite significant advances in the synthesis of nanostructures, our understanding of the growth mechanisms of nanowires and nanotubes grown from catalyst particles remains limited. In this study we demonstrate a straightforward route to grow coaxial amorphous B/BO<SUB><I>x</I></SUB> nanowires and BO<SUB><I>x</I></SUB> nanotubes using gold catalyst particles inside a transmission electron microscope at room temperature without the need of any specialized or expensive accessories. Exceedingly high growth rates (over 7 μm/min) are found for the coaxial nanowires, and this is attributed to the highly efficient diffusion of B species along the surface of a nanowire by electrostatic repulsion. On the other hand the O species are shown to be relevant to activate the gold catalysts, and this can occur through volatile O species. The technique could be further developed to study the growth of other nanostructures and holds promise for the room temperature growth of nanostructures as a whole.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2014/nalefd.2014.14.issue-2/nl404147r/production/images/medium/nl-2013-04147r_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl404147r'>ACS Electronic Supporting Info</A></P>
Ibrahim, Imad,Kalbacova, Jana,Engemaier, Vivienne,Pang, Jinbo,Rodriguez, Raul D.,Grimm, Daniel,Gemming, Thomas,Zahn, Dietrich R. T.,Schmidt, Oliver G.,Eckert, Jü,rgen,Rü,mmeli, Mark H. American Chemical Society 2015 Chemistry of materials Vol.27 No.17
<P>The search for ways to synthesize single wall carbon nanotubes (SWCNT) of a given electronic type in a controlled manner persists despite great challenges because the potential rewards are huge, in particular as a material beyond silicon. In this work we take a systematic look at three primary aspects of semiconducting enriched SWCNT grown by chemical vapor deposition. The role of catalyst choice, substrate, and feedstock mixture are investigated. In terms of semiconducting yield enhancement, little influence is found from either the binary catalyst or substrate choice. However, a very clear enrichment is found as one adds nominal amounts of methanol to an ethanol feedstock. Yields of up to 97% semiconducting SWCNT are obtained. These changes are attributed to two known etchant processes. In the first, metal SWCNT are preferentially etched. In the second, we reveal etchants also preferentially etch small diameter tubes because they are more reactive. The etchants are confirmed to have a dual role, to preferentially etch metallic tubes and narrow diameter tubes (both metallic and semiconducting) which results in a narrowing of the SWCNT diameter distribution.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/cmatex/2015/cmatex.2015.27.issue-17/acs.chemmater.5b02037/production/images/medium/cm-2015-02037h_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/cm5b02037'>ACS Electronic Supporting Info</A></P>